1. Field of the Invention
This invention relates to a method of water-proofing a connected portion of electric wires in, for example, a wire harness and the like in which stripped ends of the wires are directly coupled with each other.
2. Statement of the Prior Art
In a wire harness and the like, a connected portion of stripped ends of electric wires is subject to water erosion since a water-proof tape is merely wound around the connected portion and water is able to penetrate through gaps between turns of the wound tape into the connected portion by capillary action. In order to prevent water erosion, there are several methods of water-proofing the connected portion of electric wires.
For example, Japanese Patent Public Disclosure No. 64-6307 (1989) discloses a water-proof method in which a connected portion of electric wires is inserted in dies and melted rubber, plastic or the like is squeezed into the dies and hardened to embed the connected portion therein. Japanese Patent Publication No. 59-35510 (1984) discloses a water-proofing method in which a connected portion of electric wires is wound with a butyl rubber material and further wound by a tape or the connected portion is disposed between butyl rubber materials, then pressed by a press machine and further wound by a tape.
In addition, Japanese Utility Model Public Disclosure No. 62-123072 (1987) discloses a water-proofing method in which a connected portion of electric wires in covered with a thermal-shrinkage tube and the tube is heated to closely contact with the connected portion. Japanese Utility Model Public Disclosure No. 61-62376 (1986) discloses a water-proofing method in which a connected portion of electric wires is surrounded by split insulation covers, the covers are connected with each other at the abutted portion by an adhesive, and then bound with a belt.
Although the above prior art methods effect substantial water-proofing action, they have the following drawbacks. The method of 64-6307 requires a different die for each size and form of electric wire to be connected and high equipment costs for pressing and cooling processes. Further, the method comprises complicated steps and is difficult to work. Also, the method of 59-35510 makes the connected portion bulkier and heavier because it is covered with a butyl rubber material, which in turn requires additional time for pressing by a press machine or winding of tape.
In addition, in the method of 62-123072, it is difficult to pass the electric wire through the thermal-shrinkage tube, for example in the wire harness, and to effect mass production. The method of 61-62376 involves a high cost due to the provision of the insulation cover and makes the connected portion bulky.